The present invention relates to improvements in flexible continuous plastic zippers of the rib and groove type in which the ribs of one profile and the grooves of another profile engage when pressed together and release when pulled apart so as to form a reclosable zipper. More specifically, the present invention relates to a zipper in which the interlocking profiles themselves may be stably sealed to the packaging film of a reclosable bag thereby eliminating the need for flanges or webs as sealing areas to the packaging film. As part of the zipper, a male rib of one of the profiles can be attached to an opposing profile to form a barrier seal within the zipper.
The present invention relates to improvements in the package making art and may be practiced in the manufacture of reclosable thermoplastic bags and packages of the kind that may be used for various consumer products. Such packages often include a form of barrier seal to render the pack moistured and/or airtight prior to an initial opening of the package. A zipper with interlocking profiles protects any remainder of the product therein after the initial opening.
The prior art for zippers with interlocking profiles is fairly well developed but nevertheless remains open to improvements, specifically those which contribute to a reduction of material used in the manufacturing process. In the prior art, zippers require flanges (webs) in order to attach to the packaging film used to make a reclosable bag. In a typical sealing or attachment operation, the zipper flanges provide stability for the zipper profiles by preventing the profiles from curling in shape or contracting when heat or pressure is applied by a sealing device. An improvement to existing zippers would be to provide a zipper that does not require flanges to support the attachment of the zipper profiles in a vertical form, fill and seal (VFFS) bag making machine or other bag making machines. Without the need for flanges, the material required for the zipper and the zipper area will be reduced. With a reduced zipper area, the headspace on the packaging film required for zipper attachment will be reduced, thereby reducing the amount of packaging film required to produce the reclosable bag.
The hermetic or barrier seals of the prior art must typically be opened in order to access the zipper. The seals are positioned adjacent to the zipper and are not part of the zipper itself. An additional improvement to existing zippers would be to provide a barrier seal as part of the interlocking profiles of the zipper. An internal seal would eliminate the need for the peel sealable or barrier seal area adjacent to the zipper; thereby further reducing the amount of packaging film required to produce the reclosable bag.
Accordingly, the present invention eliminates the need for attachment flanges by improving the shape of the interlocking male and female profiles of the zipper. The improved shape comprises a male profile with at least three male ribs with two of the ribs having a double-barbed end and with the double-barbed male ribs bordering a male rib that can have but does not require a barbed end.
The female profile, which engages with the male profile, also has a plurality of male ribs. The plurality of male ribs forms two grooves, which securely interlock the double-barbed male ribs of the male profile. A bridge attaches the grooves of the female profile to each other. When the profiles are engaged and are being attached to packaging film, the end of the bordered male rib of the male profile pushes against the facing bridge and thereby pushes the bridge against the packaging film. The pressure by the bordered male rib on the bridge prevents the groove areas from curling toward each other and/or contracting during the sealing or attachment operation. Simultaneously, the bordered male rib presses against the male profile such that the bordering male ribs are prevented from curling or deforming. As a result of this pressure, a greater backing area of the male profile and the female profile can be sealed to the packaging film used to form a reclosable bag. With a greater sealed area of the profiles, the need for a backing web or flange is eliminated.
Additionally the bordered rib of the male profile may provide a barrier seal feature, wherein the end of the rib is sealed to the bridge of the female profile. An area of weakness would be provided along the bordered rib. During an opening of the zipper, the area of weakness is broken thereby providing access to the contents of the reclosable bag.